Recent Publications

Automatic event location extraction from text plays a crucial role in many applications such as infectious disease surveillance and natural disaster monitoring. The fundamental limitation of previous work such as SpaceEval is the limited scope of extraction, targeting only at locations that are explicitly stated in a syntactic structure. This leads to missing a lot of implicit information inferable from context in a document, which amounts to nearly 40% of the entire location information. To overcome this limitation for the first time, we present a system that infers the implicit event locations from a given document. Our system exploits distributional semantics, based on the hypothesis that if two events are described by similar expressions, it is likely that they occur in the same location. For example, if “A bomb exploded causing 30 victims” and “many people died from terrorist attack in Boston” are reported in the same document, it is highly likely that the bomb exploded in Boston. Our system shows good performance of a 0.58 F1-score, where state-of-the-art classifiers for intra-sentential spatiotemporal relations achieve around 0.60 F1-scores.

본 연구는 전문기관에서 생산되는 검증된 문서를 웹상의 수많은 검증되지 않은 문서에 자동 주석하여 신 뢰도 향상 및 심화 정보를 자동으로 추가하는 시스템을 설계하는 것을 목표로 한다. 이를 위해 활용 가능 한 시스템인 인공 신경 정리 증명계(neural theorem prover)가 대규모 말뭉치에 적용되지 않는다는 근본 적인 문제를 해결하기 위해 내부 순환 모듈을 단어 임베딩 모듈로 교체하여 재구축 하였다. 학습 시간의 획기적인 감소를 입증하기 위해 국가암정보센터의 암 예방 및 실천에 대한 검증된 문서들에서 추출한 28,844개 명제를 위키피디아 암 관련 문서에서 추출한 7,844개 명제에 주석하는 사례를 통하여 기존의 시스템과 재구축한 시스템을 병렬 비교하였다. 동일한 환경에서 기존 시스템의 학습 시간이 553.8일로 추 정된 것에 비해 재구축한 시스템은 93.1분 내로 학습이 완료되었다. 본 연구의 장점은 인공 신경 정리 증 명계가 모듈화 가능한 비선형 시스템이기에 다른 선형 논리 및 자연언어 처리 모듈들과 병렬적으로 결합 될 수 있음에도 현실 사례에 이를 적용 불가능하게 했던 학습 시간에 대한 문제를 해소했다는 점이다.

In this study, we propose a new system for constructing parallel corpora for sign languages, which are generally underresourced in comparison to spoken languages. In order to achieve scalability and accessibility regarding data collection and corpus construction, our system utilizes deep learning-based techniques and predicts depth information to perform pose estimation on hand information obtainable from video recordings by a single RGB camera. These estimated poses are then transcribed into expressions in SignWriting. We evaluate the accuracy of hand tracking and hand pose estimation modules of our system quantitatively, using the American Sign Language Image Dataset and the American Sign Language Lexicon Video Dataset. The evaluation results show that our transcription system has a high potential to be successfully employed in constructing a sizable sign language corpus using various types of video resources.

Background
Current state-of-the-art approaches to biological event extraction train statistical models in a supervised manner on corpora annotated with event triggers and event-argument relations. Inspecting such corpora, we observe that there is ambiguity in the span of event triggers (e.g., “transcriptional activity” vs. ‘transcriptional’), leading to inconsistencies across event trigger annotations. Such inconsistencies make it quite likely that similar phrases are annotated with different spans of event triggers, suggesting the possibility that a statistical learning algorithm misses an opportunity for generalizing from such event triggers.

Methods
We anticipate that adjustments to the span of event triggers to reduce these inconsistencies would meaningfully improve the present performance of event extraction systems. In this study, we look into this possibility with the corpora provided by the 2009 BioNLP shared task as a proof of concept. We propose an Informed Expectation-Maximization (EM) algorithm, which trains models using the EM algorithm with a posterior regularization technique, which consults the gold-standard event trigger annotations in a form of constraints. We further propose four constraints on the possible event trigger annotations to be explored by the EM algorithm.

Results
The algorithm is shown to outperform the state-of-the-art algorithm on the development corpus in a statistically significant manner and on the test corpus by a narrow margin.

Conclusions
The analysis of the annotations generated by the algorithm shows that there are various types of ambiguity in event annotations, even though they could be small in number.

Semantic fluency is a commonly used task in psychology that provides data about executive function and semantic memory. Performance on the task is affected by conditions ranging from depression to dementia. The task involves participants naming as many members of a given category (e.g. animals) as possible in sixty seconds. Most of the analyses reported in the literature only rely on word counts and transcribed data, and do not take into account the evidence of utterance planning present in the speech signal. Using data from Korean, we show how prosodic analyses can be combined with computational linguistic analyses of the words produced to provide further insights into the processes involved in producing fluency data. We compare our analyses to an established analysis method for semantic fluency data, manual determination of lexically coherent clusters of words.

Clinical depression is a complex disease, which is known to be influenced by various factors. As genetic and environmental factors are frequently referred to as the most influential in causing depression, there have been many studies that try to identify genes or proteins and environmental conditions associated with depression. While a number of text-mining (TM) systems identifying information about the genetic factors in the biomedical literature have consequently been developed, there is currently no TM system specifically targeted at extracting environmental conditions. As a result, biologists are provided only with incomplete information about depression by these TM systems, unable to help them to discover the etiology and treatment of depression. In the thesis, we propose a TM system that considers an interaction between genetic and environmental factors associated with depression. The system identifies not only relations between a sequence variation and depression but also changes in the relations according to environmental conditions. In order to develop the system, we split the system into two TM subsystems. The first system is applied to an existing system for extracting the relations between a sequence variation and depression from the biomedical literature. The system classifies whether the relations are positive or negative on a document level. Based on the dictionary with candidate terms for environmental conditions, the second system identifies the conditions in the biomedical literature containing the binary relations. Using the dependency of sentence, the system excludes terms wrongly classified as the conditions. The system is a first TM system considering a ternary relation among sequence variation, disease and condition. Through the system, we are able to provide more comprehensive information about depression than other systems. We expect that, as the system is applied to other diseases, biologists can easily identify diverse information associated with changes in symptoms of diseases including depression.

생물학적 체계 안에서 구성 요소 간의 관계를 논문 텍스트를 통해 식별하는 방법과, 일반적인 단어 사이의 관계를 분포 의미 모델을 이용하여 분류하는 방법에 대해서는 많은 연구가 각각 있었으나, 두 방법을 결합한 시도는 거의 보고되지 않았다. 본 연구에서는 분포 모델이 생물학적인 체계 안에서 두 구성요소가 맺고 있는 관계를 예측하는 데 어떤 기여를 하는지 알아보았다. 실험 결과, 분포 모델이 생물학적 구성 요소 간의 관계 식별에 유용한 자질로 활용될 수 있을 확인하였다.